Modalities in Medieval Logic
Sara L. Uckelman
Abstract:
This dissertation is an exercise in conceptual archeology. Using the
tools of contemporary logic we analyse texts in medieval logic and
reconstruct their logical theories by creating a formal framework which
models them. Our focus is medieval texts which deal with various
modalities: the writings on alethic modalities by William of Sherwood,
Pseudo-Aquinas, and St. Thomas Aquinas in the 13th century, St. Anselm
of Canterbury's writings on facere and debere in the late 11th century;
Lambert of Lagny's 13th-century treatise of supposition and its
connection to modern temporal logic; Roger Swyneshed's dynamic modality
of self-falsification, written in the early 14th century; and the
different modes of being which are expressed in statements about the
Trinity, from an anonymous, late-period text. We supplement our
discussion of these medieval texts with a historical chapter discussing
the relationship between the church and the development of modal and
temporal logic in the 13th and 14th centuries, and two appendices
containing translations into English of various source texts.
We demonstrate that by using logical tools which have been introduced in
the last quarter-century we can make better sense of the theories of
medieval logic, particularly medieval modal logic, than we could 50 or
75 years earlier, when the logician's primary tool was the mathematical
logic of Frege and Russell. The venture is also fruitful in the other
direction: We point to places where medieval responses to certain
philosophical or theological problems seems more apropos than favored
modern responses.